Petal Pigmentation Research Articles

Comparative transcriptome analyses reveal genes related to pigmentation in the petals of red and white Primula vulgaris cultivars.

Primula vulgaris is an important ornamental plant species with various flower color. To explore the molecular mechanism of its color formation, comparative transcriptome analyses of the petals in red and white cultivars was performed. A total of 4451 differentially expressed genes were identified and annotated into 128 metabolic pathways. Candidate genes FLS, F3'H, DFR, ANS and AOMT in the anthocyanin pathway were expressed significantly higher in the red cultivar than the white and may be responsible for the red coloration. In the red petals, a putative transcription factors bHLH (c52273.graph_c0) was up-regulated about 14-fold, while a R2R3-MYB unigene (c36140.graph_c0) was identified as a repressor involved in anthocyanin regulation and was significantly down-regulated. In addition, the anatomy analyses and pigments composition in the red and white petals were also analyzed. The papillae on the adaxial epidermis of the red petals of P. vulgaris display a triangle-shapes, in contrast with a spherical shape for the white petals. Although flavonoids were detected in both cultivars, anthocyanins could only be identified in the red cultivar. Gossypetin and peonidin/rosinin were the most abundant pigments in red petals. This study shed light on the genetic and biochemistry mechanisms underlying the flower coloration in Primula.

An R3-MYB gene of Phalaenopsis, MYBx1, represses anthocyanin accumulation

Anthocyanins are secondary metabolites that are involved in providing flower petal pigmentation. In plants, anthocyanin synthesis is regulated positively by a conserved MYB-bHLH-WD40 (MBW) complex and negatively by repressors. We isolated a repressor of anthocyanin synthesis, MYBx1, from a moth orchid Phalaenopsis cv. Big Chili. MYBx1 encodes a typical R3-MYB protein and exhibited diverse expression patterns in four Phalaenopsis cultivars, Big Chili, Fuller’s Sunset, Sogo Yukidian “V3”, and Sogo Lit-Sunny. A yeast two-hybrid assay analysis indicated that MYBx1 can also participate in the MBW complex by interacting with the transcription factors ANTHOCYANIN (AN) 1 and AN11. Over-expressing MYBx1 in the petunia hybrid M1 × R27 resulted in reduced accumulations of flower petal pigments through the repression of anthocyanin activities. A quantitative real-time PCR analysis of the expression patterns of anthocyanin synthesis-related structural genes in the transgenic petunia flower petals showed that the expression levels of chalcone synthase, flavanone 3-hydroxylase, and dihydroflavonol reductase genes were considerably down-regulated. However, no significant changes in the expression levels of the MBW complex members, AN1, AN2, and AN11, were observed. This study improves our understanding of anthocyanin synthesis-related regulatory networks in plants and also provides an important foundation for the further genetic engineering of ornamental plant flower colors.

Coloration and pigmentation in petals of some cyanic Ranunculus cultivars

Coloration and pigmentation in petals of some cyanic <i>Ranunculus</i> cultivars

Determination of Flavonoids and Carotenoids and Their Contributions to Various Colors of Rose Cultivars (Rosa spp.).

Rose is one of the most valuable ornamental crops worldwide. In this study, the composition of hydrophilic and lipophilic pigments in petals of six rose cultivars at seven developing stages was investigated using high performance liquid chromatography and mass spectrometry. Four anthocyanins, 20 flavonols, and 10 carotenoids were detected in petals of tested cultivars. Major individual anthocyanin, flavonol, and carotenoid were cyanidin/pelargonidin 3,5-diglucoside, kaempferol 3-O-rhamnoside, and (9Z)-violaxanthin, respectively. Significant differences were observed in pigments content in petals of different rose cultivars. The yellow petals of YI and GC exhibited no to very small amounts of anthocyanins, moderate amount of total flavonols, and highest content of total carotenoids. Similarly, pink petals of PF, WQ, and YX showed average concentration of total anthocyanins, highest concentration of total flavonols, and small amount of carotenoids. Further, orange petals of CH showed highest content of total anthocyanins, lowest content of total flavonols, and average content of total carotenoids. Correlation analysis demonstrated that there were many pigments influencing petal colors. Moreover, multiple linear regression indicated that pelargonidin 3,5-diglucoside, total anthocyanins and (9Z)-violaxanthin were the major factors. In addition, this study showed that orange cultivar CH, pink cultivar PF and yellow cultivar YI can have great potential as a natural source for the extraction of pelargonidin 3-O-glucoside, kaempferol 3-O-rhamnoside, and (9Z)-violaxanthin, respectively. These investigations would contribute toward understanding the mechanism on the development of flower colors and provide a theoretical basis for the breeding of rose with specific color.

English

English

Transcriptome-sequencing analyses reveal putative genes related to flower color variation in Chinese Rosa rugosa

Rosa rugosa is an excellent landscaping plant famous for its fragrance and primarily red flower. In this study, transcriptome sequencing on R. rugosa ‘Red Zizhi’ and its bud mutations R. rugosa ‘Pink Zizhi’ and R. rugosa ‘White Zizhi’ were conducted using the Illumina HiSeq™ 2000 platform. In total, 103,446 assembled contigs and 51,332 unigenes were obtained with average lengths of 359 and 735 bp, respectively. A total of 40,018 (77.96%) unigenes were functionally annotated; 20,054 (39.07%) of which were annotated in 128 Kyoto Encyclopedia of Genes and Genomes database pathways. Moreover, 316 (1.58%) unigenes were annotated to phenylalanine synthetic pathways related to coloration, 191 (0.95%) to flavonoid synthetic pathways and 15 (0.07%) to anthocyanin synthetic pathways. Analysis of differential gene expression profiles showed that ‘White Zizhi’ and ‘Pink Zizhi’ differed by 431 unigenes, ‘Red Zizhi’, and ‘Pink Zizhi’ by 1319 unigenes, and ‘Red Zizhi’ and ‘White Zizhi’ by 1324 unigenes. Five candidate genes were possibly highly related to the biosynthesis of rose flower pigments; they were selected by applying the differentially expressed gene method. Analyses were conducted to confirm the expression patterns of selected genes and changes and contents of flower pigments in petals of the three rose varieties in different flower development stages. Finally, by analyzing the relationship between gene expression and flower pigment synthesis, we discovered that the 4-coumarate:CoA ligase gene is possibly related to the formation of pink flowers, and low dihydroflavonol 4-reductase gene expression levels may be related to color formation in ‘White Zizhi’.

Geographic variation in pollen color is associated with temperature stress.

The evolution of flower color, especially petal pigmentation, has received substantial attention. Less understood is the evolutionary ecology of pollen pigmentation, though it varies among and within species and its biochemical properties affect pollen viability. We characterize the distribution of pollen color across 24 populations of the North American herb Campanula americana, and assess the degree to which this variation is genetically based. We identify abiotic factors that covary with pollen color and test whether germination of light and dark pollen is differentially affected by variable temperature and UV. Pollen color varies from white to deep purple in C.americana and is genetically determined. There was a longitudinal cline whereby pollen was darkest in western populations. Accounting for latitudinal variation, western populations experience elevated temperature and UV irradiance. Germination of light-colored pollen was reduced by 60% under high temperature, but dark pollen was unaffected. Exposure to UV reduced germination of light and dark pollen similarly. The cline in pollen color across the range may reflect adaptation to heat stress. This study supports thermal tolerance as a novel function of pollen pigmentation and contributes to growing evidence that abiotic factors can drive floral diversity.

Recent advances in flower color variation and patterning of Japanese morning glory and petunia.

The Japanese morning glory (Ipomoea nil) and petunia (Petunia hybrida), locally called “Asagao” and “Tsukubane-asagao”, respectively, are popular garden plants. They have been utilized as model plants for studying the genetic basis of floricultural traits, especially anthocyanin pigmentation in flower petals. In their long history of genetic studies, many mutations affecting flower pigmentation have been characterized, and both structural and regulatory genes for the anthocyanin biosynthesis pathway have been identified. In this review, we will summarize recent advances in the understanding of flower pigmentation in the two species with respect to flower hue and color patterning. Regarding flower hue, we will describe a novel enhancer of flavonoid production that controls the intensity of flower pigmentation, new aspects related to a flavonoid glucosyltransferase that has been known for a long time, and the regulatory mechanisms of vacuolar pH being a key determinant of red and blue coloration. On color patterning, we describe particular flower patterns regulated by epigenetic and RNA-silencing mechanisms. As high-quality whole genome sequences of the Japanese morning glory and petunia wild parents (P. axillaris and P. inflata, respectively) were published in 2016, further study on flower pigmentation will be accelerated.

Testing the influence of gravity on flower symmetry in five Saxifraga species.

Flower symmetry is considered a species-specific trait and is categorized in asymmetry, actinomorphic symmetry, bisymmetry and zygomorphic symmetry. Here we report on the intra-individual variation of flower symmetry in the genus Saxifraga and the influence of light, gravity and intrinsic factors on the development of flower symmetry. We tested five species-Saxifraga cuneifolia, Saxifraga imparilis, Saxifraga rotundifolia, Saxifraga stolonifera and Saxifraga umbrosa-concerning six flower parameters-angles between petals, petal length, petal pigmentation, angular position of carpels, movement of stamens and (only for S. imparilis and S. stolonifera) the length of the two lower elongated petals in regard to their position towards the stem. Specimens of all species were tested on a vertical clinostat as a gravity compensator, on a horizontal clinostat as a light incidence compensator and on a stationary control. The results show that the angle of incident light has no apparent impact on flower symmetry, whereas gravity affects the angular position of petals in S. cuneifolia and S. umbrosa and the petal colouration in S. rotundifolia. In S. cuneifolia and S. umbrosa, the absence of directional gravity resulted in the development of actinomorphic flowers, whereas the corresponding control flowers were zygomorphic. The development of flowers in S. rotundifolia was not altered by this treatment. The length of the two elongated petals in S. stolonifera and S. imparilis was not affected by gravity, but rather was determined by position of the flower within the inflorescence and resulted in asymmetrical flowers.

Fagopyrum tataricum FtWD40 Functions as a Positive Regulator of Anthocyanin Biosynthesis in Transgenic Tobacco

Tartary buckwheat (Fagopyrum tataricum Gaertn.) contains high concentration of flavonoids, which are mainly represented by rutin, anthocyanins, and proanthocyanidins. WD40 transcription factors (TFs) play significant roles in the transcriptional regulation of the anthocyanin biosynthetic pathway. In this study, a WD40-repeat protein gene (designated as FtWD40) was identified and characterized from tartary buckwheat. The bioinformatics analyses showed that the putative FtWD40 shared a high level of similarity with MtWD40-1, which is a positive regulator in anthocyanin biosynthesis of Medicago truncatula. The yeast one-hybrid assay indicated that FtWD40 had transcriptional activation activities. During florescence, FtWD40 was highly expressed in flowers compared to other organs. Furthermore, its overexpression in tobacco resulted in a remarkable deepening of petal pigmentation in flowers due to a significant increase in anthocyanins accumulation. Meanwhile, the expression of dihydroflavonol-4-reductase (DFR) and anthocyanin synthase (ANS) was upregulated 1.95- and 1.56-fold, respectively. In contrast, the expression level was lower for flavonol synthase (FLS) in the transgenic lines. To the best of our knowledge, this is the first functional characterization of a WD40 transcription factor (FtWD40) from tartary buckwheat that controls the anthocyanin pathway.

Red-purple flower color and delphinidin-type pigments in the flowers of Pueraria lobata (Leguminosae)

A previously undescribed acylated anthocyanin was extracted from the red-purple flowers of Pueraria lobata with 5% HOAc-H2O, and determined to be petunidin 3-O-(β-glucopyranoside)-5-O-[6-O-(malonyl)-β-glucopyranoside], by chemical and spectroscopic methods. In addition, two known acylated anthocyanins, delphinidin 3-O-(β-glucopyranoside)-5-O-[6-O-(malonyl)-β-glucopyranoside] and malvidin 3-O-(β-glucopyranoside)-5-O-[6-O-(malonyl)-β-glucopyranoside] were identified. Delphinidin 3,5-di-glucoside, petunidin 3,5-di-glucoside, and malvidin 3,5-di-glucoside, have been known as major components of P. lobata in the former study. However, malonyl esters amounts were detected over 10 times compared with non-malonyl esters amounts. In those anthocyanins the most abundant anthocyanin was petunidin 3-O-(β-glucopyranoside)-5-O-[6-O-(malonyl)-β-glucopyranoside] in total flowers.On the visible absorption spectral curve of fresh red-purple petals, one characteristic absorption maximum was observed at 520 nm, which is similar to those of flowers containing pelargonidin derivatives. In contrast, the absorption spectral curve of old violet petals was observed at 500(sh), 536, 564(sh), and 613(sh) nm, which are similar to those of violet flowers containing delphinidin-type pigments. Pressed juices of both fresh red-purple petals and old violet petals had pH5.2 and 5.5 respectively, and had the same flavonoid constitution. Crude fresh red-purple petal pigments extracted by pH 2.2 and pH 5.2 buffers exhibited the same color and spectral curves as fresh red-purple petals and old violet petals, respectively. Moreover, in a cross-TLC experiment of crude extracted pigments, red-purple color was exhibited by the anthocyanin region and the crossed region of anthocyanins and isoflavone. Thus, it may be assumed that the unusually low pH in the vacuole of fresh petals plays an important role to form red-purple flower color against weak acidic pH in the vacuole of old violet P. lobata petals.

Factor Analysis of MYB Gene Expression and Flavonoid Affecting Petal Color in Three Crabapple Cultivars

Flavonoid biosynthesis has received much attention concerning the structural genes and expression of the associated transcription factors (TFs). In the present study, we examined the gene expression patterns for petals of three colors using a statistical method. Factor analysis was successfully used to examine the expression patterns most present during regulation. The first expression patterns in the white and red petals were clearly demonstrated and have revealed different mechanisms of producing the proper components, whereas that in the pink petals was more complex, requiring factor analysis to supplement the other results. Combining the results of the correlation analysis between TFs and structural genes, the effects of each TF on the main expression pattern in each cultivar were determined. Moreover, McMYB10 was implicated in the regulation of the gene expression pattern in red petals, and McMYB5 was implicated in the maintenance of the balance of the pigment components and proanthocyanin (PA) production in cooperation with McMYB4 to generate pigmentation in the pink petals.

Anthocyanin biosynthesis regulation of DhMYB2 and DhbHLH1 in Dendrobium hybrids petals

Dendrobium hybrids orchid are popular throughout the world. They have various floral color and pigmentation patterns that are mainly caused by anthocyanins. It is well established that anthocyanin biosynthesis is regulated by the interplay between MYB and bHLH transcription factors (TF) in most plants. In this study, we identified one R2R3-MYB gene, DhMYB2, and one bHLH gene, DhbHLH1, from a Dendrobium hybrid. Their expression profiles were related to anthocyanin pigmentation in Dendrobium petals. Transient over-expression of these two TF genes showed that both DhMYB2 and DhbHLH1 resulted in anthocyanin production in white petals. The interaction between the two TFs was observed in vitro. In different Dendrobium hybrids petals with various pigmentations, DhMYB2 and DhbHLH1 were co-expressed with DhDFR and DhANS, which are regarded as potential regulatory targets of the two TFs. In flowers with distinct purple lips but white or yellow petals/sepals, the expression of DhbHLH1 was only related to anthocyanin accumulation in the lips. Taken together, DhMYB2 interacted with DhbHLH1 to regulate anthocyanin production in Dendrobium hybrid petals. DhbHLH1 was also responsible for the distinct anthocyanin pigmentation in lip tissues. The functional characterization of DhMYB2 and DhbHLH1 will improve understanding of anthocyanin biosynthesis modulation in Dendrobium orchids.

Components of Flower Pigments in Petals of Lily

This paper carried on a preliminary study on pigment composition of lilies of different colors by means of specific color reactions and UV-visible spectra. The results showed that the colors of lilies were usually caused by the combined action of several pigments; yellow and orange lilies mainly contained the flavonoids and carotenoids; pink lilies mainly contained flavonoids and anthocyanins, and white lilies contained small amount of flavonoids.

Light quality impacts on growth, flowering, mineral uptake and petal pigmentation of marigold

Light quality has a significant impact on growth and development and time to flower in many plant species. Recently, the percentages of blue and red in narrow-band wavelengths of light from light-emitting diodes (LEDs) have been shown to impact mineral uptake, pigment development and the rate of growth and development of several plant species. The objective of this research was to evaluate the effects of light quality on shoot growth, flower development, mineral uptake and pigment content of marigold (Tagetes patula 'Safari Orange'). Plants were grown in 10-cm square pots in a greenhouse ebb and flood system with a complete nutrient solution. Plants received average day temperatures of 25°C and night temperatures of 16°C. The following light treatments were utilized in this study: 1) natural sunlight; 2) high-pressure sodium (HPS) lighting at 100 µmols m-2 s-1 intensity in addition to natural sunlight intensity; 3) LED lighting with blue and red wavelengths at 50% each and intensity at 100 µmols m-2 s-1 in addition to natural sunlight intensity; and 4) LED lighting with blue at 25% and red at 75% and intensity at 100 µmols m-2 s-1 in addition to natural sunlight intensity. Total shoot growth was twice as high in all supplemental light treatments compared to the natural sunlight treatment. Shoot growth was greater in the 25% blue/75% red LED treatment than in the HPS light treatment. The 50% blue/50% red LED treatment was not significantly different from the HPS light treatment. Plants in the 25% blue/75% red LED treatment had 15% more blooms than plants in the 50% blue/50% red LED treatment or the HPS light treatment. All supplemental light treatments produced plants with significantly more blooms than plants in the natural sunlight treatment. Plants in the LED light treatments had greater petal pigment content than plants in the natural sunlight treatment.

Genotype and lighting environment impact petal tissue pigmentation inTagetes tenuifolia

Genotype and lighting environment impact petal tissue pigmentation in<i>Tagetes tenuifolia</i>

Selection of Reference Genes for Quantitative Real-Time PCR during Flower Development in Tree Peony (Paeonia suffruticosa Andr.).

Tree peony (Paeonia suffruticosa) is a perennial plant indigenous to China known for its elegant and vibrantly colorful flowers. A few genes involved in petal pigmentation have been cloned in tree peony. However, to date, there have been few studies on the comparison and selection of stable reference genes for gene expression analysis by quantitative reverse-transcription PCR (qRT-PCR) in this species. In this study, 10 candidate reference genes were evaluated for the normalization of qRT-PCR in three tree peony cultivars. GAPDH and UBC were identified as the top two most stable reference genes in ‘Feng Dan’ and ‘Xi Shi,’ and EF-1α/UBC was recommended to be the best combination for ‘Que Hao.’ The expression stability of various reference genes differed across cultivars, suggesting that selection and validation of reliable reference genes for quantitative gene expression analysis was necessary not only for different species but also for different cultivars. The results provided a list of reference genes for further study on gene expression in P. suffruticosa. However, in any case, a preliminary check on the accuracy of the best performing reference genes is requested for each qRT-PCR experiment.

Molecular phylogenetics of the Ronnbergia Alliance (Bromeliaceae, Bromelioideae) and insights into their morphological evolution

The tank-epiphytic clade of berry-fruited bromeliads, also known as the Core Bromelioideae, represents a remarkable event of adaptive radiation within the Bromeliaceae; however, the details of this radiation have been difficult to study because this lineage is plagued with generic delimitation problems. In this study, we used a phylogenetic approach to investigate a well supported, albeit poorly understood, lineage nested within the Core Bromelioideae, here called the “Ronnbergia Alliance”. In order to assess the monophyly and phylogenetic relationships of this group, we used three plastid and three nuclear DNA sequence markers combined with a broad sampling across three taxonomic groups and allied species of Aechmea expected to comprise the Ronnbergia Alliance. We combined the datasets to produce a well-supported and resolved phylogenetic hypothesis. Our main results indicated that the Ronnbergia Alliance was a well-supported monophyletic group, sister to the remaining Core Bromelioideae, and it was composed by species of the polyphyletic genera Aechmea, Hohenbergia and Ronnbergia. We identified two major internal lineages with high geographic structure within the Ronnbergia Alliance. The first of these lineages, called the Pacific Clade, contained species of Aechmea and Ronnbergia that occur exclusively from southern Central America to northwestern South America. The second clade, called the Atlantic Clade, contained species of Aechmea, Hohenbergia and Ronnbergia mostly limited to the Atlantic Forest and the Caribbean. We also explored the diagnostic and evolutionary importance of 13 selected characters using ancestral character reconstructions on the phylogenetic hypothesis. We found that the combination of tubular corollas apically spreading and unappendaged ovules had diagnostic value for the Ronnbergia Alliance, whereas flower size, length of the corolla tube, and petal pigmentation and apex were important characters to differentiate the Pacific and Atlantic clades. This study opens new perspectives for future taxonomic reorganizations and provides a framework for evolutionary and biogeographic studies.

Standardization of dehydration technique for greenhouse cut rose var. Shakira

An investigation was conducted to evaluate optimum dehydration technique for greenhouse cut rose var. Shakira at different harvest stages, viz., bud stage, 50% open and fully opened flowers. Flowers dried at 50% open stage showed higher retention in dry weight and flower diameter though flowers dried at fully opened stage took minimum time to drying process. Among various drying techniques, microwave oven with silica gel as embedding medium took minimum time in drying and showed higher moisture loss, lower moisture content and higher dry weight, flower diameter and petal pigment retention. Further, among all treatment combinations, flowers dried at 50% open stage in microwave oven embedded with silica gel as embedding media showed best quality in terms of higher retention in dry weight, flower diameter, petal pigments (anthocyanin) along with well-maintained shape, smooth petal texture and maximum dry flower longevity.

Floral Pigmentation and Expression of Anthocyanin-Related Genes in Bicolored Roses ‘Pinky Girl’ as Affected by Temporal Heat Stress

Abstract: This study was conducted to investigate petal pigmentation and the expression patterns of anthocyanin-related genes in bicolored roses ‘Pinky Girl’ treated with temporal heat stress (THS). Cyanin accumulation in petals was correlated with flor al bud development and started rapidly as floral buds began to open, defined as the 4 th stage of floral bud development (S 4 ). This stage seems to be most susceptible to petal pigmentation. The total of cyanin pigmentation at blooming was si gnificantly decreased (by 45.5%) with exposure to THS (39/18°C for three days at S 4 ) in comparison with control. Meanwhile, the expression of anthocyanin-related genes such as CHS, CHI, F3’H, DFR, ANS, 3GT, and 5GT was relatively promoted by THS. Only F3H was less expressed (by 26.7%) with THS treatment; thus, F3H could be a key gene for bicolor promotion in ‘Pinky Girl’ amon g anthocyanin-related genes. Overall, the expression pattern of the most anthocyanin-related genes did not match the trends of cyanin pigmentation in petals. These results suggest that floral pigmentation could be associated with other mechanisms related to anthocyanin biosynthesis such as post-translational effects and regulatory genes.Additional key words: